Endothelial Keratoplasty

What is the cornea and what role does it play in my vision?

The cornea is a transparent tissue that acts as the front window of the eye, covering approximately the width of the coloured iris. It plays a vital role in focusing light onto the back of the eye, allowing us to see.

What makes up the cornea?

Our cornea is made up of three major layers: the outside, epithelial layer; the middle, or stromal layer, and the inner, endothelial layer.

How can my vision be affected by my cornea?

Through a variety of disease processes, the cornea can become swollen or scarred, resulting in a loss of transparency and good vision. In some cases, the endothelial cells of the cornea can be damaged or degenerate. The function of the endothelial cells is to pump fluid out of the cornea, maintaining its clarity. When many endothelial cells are injured or lost, the cornea is unable to pump fluid out, causing it to swell with fluid and lose its transparency. When this occurs, while medications may help, surgery is often required. A corneal transplant may also be recommended.

Full Thickness (penetrating keratoplasty) vs. Partial Thickness (endothelial keratoplasty)

With traditional full thickness transplant surgery (known as Penetrating Keratoplasty), the entire central portion of the cornea is removed and a donor cornea is sutured into place. It may take one year or more to recover from a full corneal transplant. Additionally, it is possible to develop an irregular curvature of the cornea caused by the stitches, leading to a condition known as astigmatism, which may or may not be correctable with hard contact lenses. Finally, there is a risk of transplant rejection and injury to the cornea.

Depending on the corneal condition you have, a partial thickness corneal transplant, or Endothelial Keratoplasty (EK), may be a better option. If the epithelial and stromal layers of the cornea remain clear and only the endothelial cells are compromised, an EK may be considered to improve your vision.

With a partial thickness transplant, only the compromised tissue of the cornea is removed. A thin disc of donor tissue containing healthy endothelial cells is then placed on the back surface of the cornea. An air bubble pushes the endothelial cell layer into place until it heals in an appropriate position.

The EK surgical procedure is quicker, requires a smaller incision, uses fewer stitches, has a shorter recovery time, and restores vision faster than with traditional corneal transplant. Also, because fewer stiches are used, there is a lower risk of developing astigmatism, and since less tissue is transplanted, there is a lower rate of transplant rejection. Finally, since the entire top of the cornea remains intact, EK is a safer surgical procedure compared with conventional full thickness corneal transplant surgery.